1. Field of the Invention
This invention relates to a novel process for the preparation of crystalline, synthetic molecular sieve materials and materials so produced.
2. Summary of the Invention
By `molecular sieve` is meant herein microporous three dimensional framework materials having pores generally in the 2 to 20 Angstroms size range which are capable of use for molecular separations. The framework may consist of or comprise, for example, aluminosilicate, aluminophosphate or silica.
According to one aspect of the present invention there is provided a process for the production of a synthetic crystalline molecular sieve material characterised by the use in the reaction mixture of an organic template comprising an optically active enantiomer. It has now been found that by the use of the novel templates described above the synthesis may be controlled to produce different products than would be produced using the corresponding racemic form of the template and that novel zeolites may be produced thereby.
The present invention is particularly, although not exclusively, concerned with the preparation of high silica zeolites or their silica analogues. By "high silica zeolite" is meant a zeolite having the general formula: EQU xR.sub.2 O:yM.sub.2 O.sub.3 :zSiO.sub.2 :wH.sub.2 O
where R is one or more alkali metal or alkaline earth metals of valency n preferably sodium, M.sub.2 O.sub.3 is an oxide of one or more of B, Al, V, Cr, Mn, Fe, Ga, As, Mo or Sb but preferably Al, x is a charge balancing quantity of R, y is from 0 to 1, z is more than 6, for example from 10 to 5000 and W is at least 0 for example from 0 to 2000. While zeolites having a lesser content of silica such as the traditional zeolites A, X and Y may be manufactured readily without the assistance of an organic template material high silica zeolites are generally synthesised with the assistance of an organic template material present in the reaction medium. Such synthesis may be accomplished by including sources of the constituents of the zeolite in an aqueous reaction medium containing the template material and heating, generally, under elevated pressure until crystallisation has taken place. Very suitably the proportions of the sources of the constituents are such as to provide a reaction medium having the following composition in terms of oxide mole ratios. ##EQU1## where R, and M have the values above defined. Suitably, the alkali metal may be provided by the hydroxide and/or by the use of an alkali metal silicate; the SiO.sub.2 may be provided by the use of a silica hydrosol or gel, by silicic acid or by said sodium silicate; and the metal M may be provided by the sodium metallate, for example, aluminate or by the use of a metallosilicate, for example aluminosilicate. Alternative sources of the desired ingredients will be well known to those versed in the art. Suitably, the synthesis may be carried out under alkaline conditions, at a temperature of from 100.degree. C. to 300.degree. C. and at a pressure of from about 1 to 100 bars which may, if desired, be generated autogenously. The zeolite so formed may be separated, washed free of residual reaction medium, dried and calcined to remove residual template materials and/or to reduce or remove water of crystallisation.